TUESDAY, June 7 (HealthDay News) -- Testosterone levels don't necessarily drop with age, but it's more likely among older men with declining general health, a new study suggests.

Bucking prior research indicating age-related testosterone deficiency contributes to deteriorating health, fatigue and libido loss, Australian researchers found that blood testosterone amounts didn't fall in older men with optimal health.

The data, gathered as part of the Healthy Man Study, is scheduled to be presented Tuesday at the Endocrine Society's annual meeting in Boston.

"Our interpretation is that age in and of itself does not reduce blood testosterone levels . . . but the accumulating disorders as men age, some preventable and some not, some genetic and some environmental, do have such an impact, albeit pretty modest," said study author Dr. David Handelsman, a professor of reproductive endocrinology and andrology at the University of Sydney.

"This would make the drive for testosterone treatment for the well-known -- but overrated -- age-related decline in blood testosterone misguided," added Handelsman, also director of the university's ANZAC Research Institute. "But, of course, we could be wrong."

Handelsman and his team took blood samples nine times over three months from 325 men over age 40 who reported being in excellent health. Men who took medications that affect testosterone were excluded from the research.

While age had no effect on testosterone concentrations, obesity was linked to a minor decline, the scientists said.

Dr. Ronald Swerdloff, chief of the division of endocrinology at Harbor-UCLA Medical Center in Los Angeles, noted that other studies had documented a greater drop in testosterone among older men and called Handelsman's research "a piece of the puzzle."

"Many people agree that acute and chronic illness will adversely affect blood testosterone levels, so that's not a surprise," said Swerdloff. "But there are reductions that seem to be independent of co-morbid conditions. The fact of the matter is, with an increase in age [comes] a decrease in testosterone levels, [but] the degree of fall differs from study to study, and the variation could be due to many factors."

Swerdloff said he doesn't support companies who try to profit from older men's fears of declining testosterone by selling supplements that purportedly offset the drop.

"Theoretically, they're exploiting the population and taking advantage of a condition that may be real, but not universal, in order to gain financial reward," he said.

Because this study was presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.